Currently it is necessary to go to a separate website, the URL is: http://gatheringvolumes.papertrell.com/ and there you can use the links to download the app to your phone or tablet (includes Nook, Kobo, or Fire). You will not be able to download to a Kindle since they use Amazon's propriety e-books.

Once you download the app you can purchase books from the website to read or listen to on your device. You can also read or listen to free samples and free titles in the app.